*{
    margin: 0 auto;
    padding: 0;
    background: black;
}

img{
    width: 100%;
    height: 100%;
    border-color: #666;
    border-right-color: #4e6ef2;
}
.tw{
    width: 100px;
    height: 60px;
    color: bisque;
    text-align: center;
}    
/* jay框 */
.jay{
    width: 1700px;
    height: 400px;
    /* 大框背景 */
    background-image:url(./tu/beijing.jpg);
    padding: 10px;
    margin-top: 10vh;
    overflow: hidden;
}
.a{
    font-family: serif;
    text-decoration: none;
}
.jay ul li{
    /* list-style: none; */
    position: relative;
    float: left;;
    width: 200px;
    height: 200px;
    margin: 5px;
}
.big{
    display: none;
    border: radius 5px;
    width: 390px;
    height:200px;
}
.small{
    /* display: none; */
    position: absolute;
    top: 0;
    left: 0;
    width: 200px;
    height: 200px;
    border-radius: 5px;
}
.bigbox ul .to.big{
    display: block;
    /* 大图显示 */
}
.bigbox ul .to.small{
    display: none;
    /* 小图隐藏 */
}
.bigbox ul .to{
    width: 200px;
}